1. Field of the Invention
This invention relates to a time recorder, and more particularly to a technique to compensate for commerical power supply interruption in a time recorder having a digital display and an analog display.
2. Description of the Prior Art
A time recorder in which an electronic clock is used as a clock system employs the commercial power supply as a source of energy for operation thereof since the time recorder necessitates a high electric power for its operation due to the fact that rotation of a steeping motor is transmitted to drive printing wheels in a timed relationship via several wheels and a ratchet mechanism and printing operation is effected by a hammer which is actuated by a solenoid.
Accordingly, in a conventional time recorder, a countermeasure when the supply of the commercial power is inadvertently shut down due to service interruption or disconnection of a power supply plug, a digital display device, an analog display device and a time printing mechanism are stopped while only a clocking function is kept operative by a backup cell, and then upon recovery of the commercial power supply, the present time is indicated on the digitial display device while the analog display device and the time printing mechanism are caused to move momentarily until respective reference positions thereof are found out and then correcting operations are carried out when the present time coincides to the reference position. When the power supply interruption occurs frequently, there are problems that a considerable time is required for such correcting operations, a mechanism for detecting the reference positions is required and the present time cannot be observed during the commercial power supply interruption.
In another conventional time recorder which includes both a large size hand-type time display mechanism and a digital display mechanism which normally indicates the month and day, the commercial power supply is employed as a driving energy source because a high driving force is required for the hand-type time display mechanism. On the other hand, the digital display mechanism requires only a low power consumption and is thus backed up by an auxiliary power source such as a battery to continue the indication of the month and day. However, since the time is no more indicated, it is a problem that the clock is inconvenient to a user. In order to eliminate such a problem, it may be possible to change over the contents of indication of the digital display mechanism from the date to the time so that a user may not feel inconvenience. However, there still is a problem that, regardless of the commercial power supply interruption, a user may unconsciously recognize the incorrect indication of the analog display mechanism as the present time due to the form of indication which has been normally familiar to the user.
The conventional time recorder in which an electronic clock is used as a clock system employs the commercial power supply as a source of energy for operation thereof since it necessitates a high electric power for its operation due to the fact that rotation of a stepping motor is transmitted to drive printing wheels in a timed relationship via a wheel train and a ratchet mechanism and printing operation is effected by a hammer which is actuated by a solenoid.
Accordingly, in the conventional time recorder, there is a problem that when the supply of the commercial power is inadvertently interrupted due to service shut-down or disconnection of a power supply plug, a wheel train and a ratchet mechanism during rotation will be halted midway so that, upon recovery of the commercial power supply, they will start from incorrect positions thereof, and hence upon subsequent printing operation, the printing wheels and a card feed mechanism will not stop at correct positions, resulting in printing error.
Another conventional time recorder normally employs the commercial power supply as a source of energy since it drives a high mechanical load such as a printing wheel and a hammer while a clock circuit wherein power consumption is relative low is backed up by an auxiliary power source such as a battery to obtain an accurate time signal regardless of the commercial power supply interruption so that, upon recovery from the service interruption, the printing wheel may be automatically corrected to the present time in accordance with the time signal.
By the way, it is sometime necessary, for example, upon shipment from a factory or for a business talk, to demonstrate that, after the service interruption, a printing wheel and/or an analog display mechanism are automatically corrected to the present time. In such a case, normally an operation is required to arbitrarily interrupt the supply of the commercial power supply and keep it interrupted for a sufficient interval of time to allow a sufficient difference to appear between the printing wheel and/or analog display mechanism and a time reference signal and thereafter to supply the power again to cause the printing wheel and the analog display mechanism operative. Therefore, it is a disadvantage that there is considerable waste time.